Abstract: A smoothing method for noisy measurements based on optimal knots spline is presented.Describes the objective movement using the B spline with free knots,and in terms of the least square principle,the optimal knots distribution is searched employing the nonlinear optimization.Consequently,the approximative process is adaptively fit for the objective movement,and the approximative precision is improved.The ideal smoothing and differentiation smoothing effect can be obtained even if the object moves rapidly.